The large number of overweight children in the U.S. has led school administrators and researchers to examine how aspects of the school environment affect children's dietary behavior and health. In addition to consuming nutrient rich food and exercising regularly, nutritionists have suggested that it is important for children to have an adequate amount of time to eat meals. This is because individuals only begin to feel full twenty minutes after they start eating, and as a result, those with a short meal period are more likely to overeat because they do not recognize that they are full within the meal period. This paper examines whether the length of time children are assigned to eat lunch in school has an impact on their nutritional health (as measured by BMI) using data from the School Nutrition Dietary Assessment-III. A parsimonious OLS specification suggests that a ten minute increase in a child's assigned lunch length significantly decreases the probability of being overweight by 1.83 percentage points and reduces BMI by 0.187 points. These results may be biased if there are unobserved characteristics of children and/or schools which are correlated with lunch length and are predictors of BMI. I address this endogeneity in two ways: First, I include an exhaustive set of controls for schools' nutrition policies and children's diet and exercise behavior that are intended to proxy for these unobserved characteristics. The results indicate a similar impact of lunch length: A 1.86 percentage point decrease in the probability of being overweight and a 0.194 reduction in BMI. Second, I include school fixed effects which control for factors that are common to children attending the same school, and find a 10 minute increase in lunch length predicts a 0.227 point decrease in BMI. Although the identification strategy cannot control for the non-random selection of children into schools, the proximity of these estimates to the initial results suggests that there is indeed a negative impact of short lunch length on health. Moreover, this observed relationship does not seem to be explained by unobserved differences among children and schools with different lunch lengths.